Conservation of energy and the use of renewable energy sources have become increasingly urgent goals worldwide. Thus much research is being devoted to studying the means whereby naturally available solar radiation may be converted to thermal wavelengths at temperatures appropriate for direct use or storage. The conversion of light to heat, notably direct sunlight at wavelengths of 0.3 to 0.8 microns converted to infrared wavelengths of 0.8 microns to 3000 microns, has been accomplished in many endeavors.
Of these efforts, roof or wall-mounted collector panel systems, though highly successful in conversion by attaining high absorber temperatures, suffer from excessive loss to the exterior ambient as the temperature differential (.DELTA.t) between opaque absorber surfaces and outdoor temperature increases. These panel systems also require extensive manifolds, insulation and structural support against windloads.
Thus it has been considered desirable to integrate collector systems into the external walls of a building. This was first accomplished by the Trombe-Michel wall in Odeillo, France, 1967, wherein an exterior sheet of flat glass in frames, formed the outer transparent boundary of a planar air manifold in which the interior boundary of the manifold was provided by a monolithic 12" concrete mass. The concrete, by virtue of its natural absorptive and emissive characteristics, converts incident sunlight into thermal energy, part of which is transferred to the convective air current moving over the masonry surface and part moves thru the concrete mass in a heat wave with an 8 hour time lag for radiation benefits to the interior. The convective warming airstream expands naturally through the planar manifold and pushes its way out of the manifold at the top of the rise through exit vents into the interior living space, where it loses its heat and drops to the floor. The cool air layer at the floor drops into the entry vents of the Trombe manifold where the hot air thermosiphon repeats its natural collection cycle at a relatively slow air velocity.
The advantages of the Trombe lie in the natural expansion of the air in x and y directions through the planar manifold and its natural exit and entry in the z direction, thereby integrating the collector flow directly with the thermal loops of the interior ambient. The interior air volume to be heated exchanges directly through the Trombe manifold which is also the southern wall of the building thus integrating collection with the building skin and structure and thereby obviating the need for secondary manifolds.
However, the disadvantages of the Trombe are cited here for the purpose of introducing the present invention. First, the heat wave moving through the opaque mass of concrete has an 8 hour time lag before it reaches the interior surface. Thus the interior living/work space behind the Trombe is dark and the wall is relatively cool to touch during collection cycle. Further, the Trombe itself is opaque, and although windows may be located in the absorber mass for direct gain, it is not possible to see through the Trombe. Also, extensive framing is required to sustain the exterior glass panes. The entire wall configuration, to date, has been built by on-site assembly of flat glass placed over standard masonry units or poured in place masonry. Further, the surface area of the flat masonry wall available for absorption, limits the surface area available for convective transfer to air flowing over its surface. The thermal gradient between the warm concrete surface and the outdoor temperature is subject to the same loss to exterior ambient as are the typical metal collector panel systems.
To date Trombe walls have not been considered suitable for multi-story collection due to extensive structural framing required to support the exterior glass. Also, multi-story collection implies excessive overheating of the air flow and overheating of the absorber surfaces due to cumulative incidence over an extended rise or flow path. This overheated condition and consequent loss to exterior, is caused by conversion of incident energy and transfer from an absorber surface that is opaque or which has insulation between the absorber and the interior ambient.
Further, when heat mirror coatings are placed on surface 2 or 3 of the outer double pane glass, the temperature is increased in the multi-story airstream, thereby exacerbating the (.DELTA.t) temperature differential between the absorber masonry or other opaque conversion surface and the exterior ambient. Thus, because of opacity of the absorber surface, an excessive temperature build-up occurs in the collector air space which is not made available to the interior ambient or modulated by other means and thus loss occurs to the exterior due to high (.DELTA.t).
Therefore, the present invention proposes to provide a convective multi-story collector wall and roof system, with expanded Trombe-Michel flow patterns, that is easily assembled by combining a plurality of communicating building components and which has a low (.DELTA.t) loss by conductance to the exterior due to provision of transparent and semi-transparent interior boundaries for the planar manifold flow.
Thus an entirely transparent collector warm airstream bounded by alternating conversion and transparent planar manifolds is envisioned, made possible by multi-story cumulative incidence and the rise of the airstream through interspersed, adjacent, communicating absorber cavities and transparent cavities.
The planar manifold is comprised of building block components, transparent and opaque, which fit together to form multiple hollow flow cavities which communicate in x, y, z directions. The airstream thus passes over both primary absorber conversion surfaces and secondary convective transfer surfaces provided by internal cavities, or through multiple planes of flow separated by transparent boundaries.
All components of the proposed building system being modified to retain their load bearing or self-sustaining capacity while providing both the exterior transparent boundary for Trombe flow and also the interior absorber conversion boundary, which may be transparent for temperature control, semi-transparent for conversion, or opaque for conversion when loadbearing.